I bought a 12V, 7.2AH sealed lead acid (SLA) battery from Amazon (link).
As a reference for the required charging curve I'm using the chart from page 7.38 of the 2023 ARRL Handbook. See graph below. For Stage 1 current I use C/10, for 0.72 A. Topping charge voltage will be the bottom of the Handbook guide of 2.3V to 2.45V per cell, i.e., 13.8V. This is in accordance with voltage recommendations on the side of the battery. Float voltage will be 13.5V. So summarizing:
- Stage 1: constant current 0.72A
- Stage 2: constant voltage 13.8V
- Stage 3: constant voltage 13.5 V
I am in the process of designing the charging circuit now. I have ordered some UC3906 Lead Acid charger controller ICs from Amazon (link). I've also ordered XL4015 based buck converters (Amazon link). These buck converters can be programmed for an output voltage and current limit that will produce multi-stage charging. I'm also thinking of using a LT3652 IC based module (Amazon link)
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